Cherry Pi III Is Available

Matt, the IR probe should give a reading of about 465 at a height slightly above the trigger height, when the LED is off but only just.

If your buid is accurate and the probe points are symmetrically placed, then probing may provide insufficient data to get good calibration of the diagonal rod length. I suggest you switch to 6 factor calibration, by changing S7 on the final G30 command in bed.g to S6. Alternatively, add more bed probe points. I use 13 on my large Kossel. The maximum supported is 16.

Thanks for the info, So that would be P0 to P15, and P15 being the last G30 P15 X0 Y0 Z-99999 S7.

Thanks

Matt

Yes, that's right.

I'm coming to the opinion that it's probably not worth adjusting the diagonal rod length during auto calibration. It's the one parameter that you should be able to get spot-on. When I use 6- instead of 7-factor calibration, the RMS error increases only slightly. If the diagonal rod length gets adjusted too much, then the XY scaling will be wrong.

Ok I guess this is a bit out of date but I finally got my version of cherry pi ii up and running. lol

Based on cherry pi ii with the following differences.
P2 carriages but redesigned to incorporate a pinch bolt so any lateral play can be adjusted out.
(I found the original P2 carriages became loose on the extrusion after some use.)
Redesigned centre and carriage plates to use standard ball links.
Direct drive bowden extruder.
My own design heated bed. made from 250mm dia x 4mm round mirror (I think these are used as wedding reception table platters) and 4M of resistance wire cut into 4 separate heaters wired in parallel.
Final resistance is 1.5 ohms pulling about 8amps or say appx 100 watts. I basically just stuck the resistance wire on the back of the mirror in a spiral pattern with capton tape. It works very well.
I haven't incorporated auto bed leveling yet but may try it at some point but manual bed leveling is a breeze with this printer once the delta kinetics are sorted.
Mega2560 -Ramps1.4 and marlin.
I am extremely pleased with this printer and my poor old prusa i3 has had very little use since the delta was finished
Thanks to Andy for a great basic design!!
Some pics

Are they good bad or ugly, They look pretty good to me but I would like other peoples opinions, is there anything I need to look at? The bed Radius is set to 90, although it is a 260 diameter bed, the IR sensor falls off the end of the build plate if I have this set to 130. So I set all my cal points to a 90 bed.

Matt, those figures look not too bad to me, although the RMS error you are getting is a little high. I suspect that the effector is tilting slightly as it translates. I had the same problem initially.

Also, your Y and Z endstop corrections are varying by rather a lot, which suggests to me that you are not getting consistent results from microswitches or from the sensor. The initial probing speed is set by the M210 Z parameter. The final probing speed is equal to the Z maximum jerk speed, set by the M566 Z parameter. I've just realised that I increased the jerk speeds set in config.g recently, forgetting that they affect Z probing as well. So I suggest you reduce the M566 Z parameter to 200 in config.g. I just did this, and at the same time reduced the F500 parameter in line 6 of homedelta.g to F250, to reduce the final homing speed. These changes have improved reproducibility for me. I now get these results:

You can also test whether the sensor is giving consistent results like this. Take a copy of your bed.g file, remove the G28 homing commands from the start and end (to eliminate the effect of endstop switch jitter), and replace S6 in the final G30 command by S0. This will perform no calibration but instead print out the height errors at all the probe points. You can run this several times and compare the results.

Yes, those results look more stable. It seems to be needing 2 iterations to converge, and you have nearly 1mm difference between your Y and X endstop corrections. So I suggest you adjust your endstops slightly to reduce the corrections needed, also set your delta radius to about 150.85mm in config.g.

It might also be worth checking for effector tilt. I do this by putting the nozzle on the verge of touching the bed at various points, and then checking the height of the sensor board edge above the bed using feeler gauges.

QuoteMatt,Wheatley
I tried to modify the bed.g as you suggested, by removing the G28 from the beginning and end and changing the S6 to S0 , I get the following error:

Just thought I'd pop my head in and say hi as I've started collecting parts to build my own Cherry Pi III. It'll be my first 3D printer, although I've backed The Micro on Kickstarter. I'm definitely going to need some help so I figured I'd introduce myself first!

So far the biggest challenge has been to locate parts within Australia as shipping really is a killer for anything from the UK or the US. I think there was one order I got quoted on and it was around US$100 just in shipping alone and it wasn't even a large amount of parts! I did decide to get my plastic parts from Andy... not only as a bit of a thank-you for putting this project out in the wild but because I think he'll take a fair bit of care to make sure they're on-spec. One day, when I get a bit more adventurous, I'd love to try and cast some modified versions of the components (removing unnecessary material due to added strength of aluminium) using the lost-PLA method... but that might be a bit down the track.

In terms of parts sources I'm going with:
- Plastics and some items I was unsure about (springs, bearings, etc) from Andy
- V slot, pulleys and mini v wheel kit from OpenBuilds
- GT2 belt and smart LCD controller (seems the same as the RRD one?) from BilbyCNC
- RAMPS, Mega2560, stepper drivers and NEMA 17s from MorelliTech
- Most of the fasteners from bolt.com.au if I can't get them at a similar price from Masters or Bunnings
- Power supply from RS (unless I can find cheaper)
- Centrifugal fan from Element14
- A few other things like aluminium tube from smallparts.com.au

It's a lot of different sources but places like RS and smallparts I can access in person, so it won't set me back on shipping.

My main goal is to have something with a good sized print area that can do some pretty reasonable resolution prints. The Micro is going to be cool to do small parts but I want to do some bigger stuff too.

One idea I've been tossing up is to build a large enclosure for it, just to a) absorb the small amount of noise it seems to make and b) to potentially warm up the area a tiny bit. I don't think I'll go full heat bed but I'm considering feeding a small, not-fan-driven heater to have a heated chamber of sorts. Would that cause any issues with the components?

I'm really excited, should be a great project and produce some nice parts!

Hahah, you guys. I FINALLY FINISHED IT. Only took like 10 months and around 50 hours troubleshooting.

Okay, so there's a bit of fine tuning to go, but I've finally got parts that stick to the bed and get printed fully and correctly.

The biggest problem was that at some point unbeknownst to me, I'd set the Z probe offset to being 0.8mm. That meant that although the paper calibration worked it was 0.8mm off in the centre. So stupid. It now prints though!

A few questions...
- After I do the fine tuning calibrations, where's the best place to ask about improving my print settings? I noticed they're a bit messy so I'd like some pointers to what I should be tweaking to fix a few things.
- Also, what's the latest and greatest methodology for adding a heated bed? I've got a M3D Micro too and it suffers from curling something terrible (event smallish PLA) so I'd like to heat my bed.

I think I'll actually place the heated bed under my existing glass bed. I'm not sure how I'll attach them yet but I guess it'll involve a fair amount of thermal paste. It's probably going to be overkill but as long as I pre-heat it (so that the glass is the same temp as the bed thermister is reading) it should work fine. Theory being that the more heat that's being held by the plate, the less likely it'll be affected by ambient cooling (aluminium is a great conductor of heat but also cools quickly too... glass is a little more resistant to all kinds of change).

I'm a tad worried about if the new PSU will fit into the rig but it's only ~4cm longer, ~1cm wider and ~1cm higher than the original 60W I had. Here's hoping.

Quotepugzor
The biggest problem was that at some point unbeknownst to me, I'd set the Z probe offset to being 0.8mm. That meant that although the paper calibration worked it was 0.8mm off in the centre. So stupid. It now prints though!

A few questions...
- After I do the fine tuning calibrations, where's the best place to ask about improving my print settings? I noticed they're a bit messy so I'd like some pointers to what I should be tweaking to fix a few things.
- Also, what's the latest and greatest methodology for adding a heated bed? I've got a M3D Micro too and it suffers from curling something terrible (event smallish PLA) so I'd like to heat my bed.

Hi @pugzor,

Well done for getting to this stage.

1) To reset the Z height, if you haven't already found it, send some GCODE to the printer as follows:

M666L
This lists the current setting. Find the H value and subtract 0.8 from it then send:

M666 HNewValue

2) If you use something like BuildTak as @DeeJay suggests, you'll be able to print PLA without a heated bed. BuildTak is quite expensive but lasts a long time if you treat it carefully when prising the prints off. I used to do it this way but then I changed to printing on 200mm circular glass on top of a heated bed at 55-60C. Just get some hairspray that includes some polymer in the ingredients (I use Elnet Satin Super Hold from Tesco - in the UK). Just a light spray about every 5 prints does the trick. The great thing with this glass/hairspray combo, compared to BuildTak where the print sticks like glue, is that the print just "pops off" when the bed cools below 30C.

I'm not sure which version of the CPi you have but if you're using the the latest version with the inductive probe you may find that adding a 2-3mm glass bed over the aluminium base will take the probe out of range. In this case, you might have to just use the probe for calibration (with the glass removed - and then adjust the Z height by the glass thickness as mentioned above) and disable the levelling before every print.

@bower-andy, that's exactly what I did re: Z-probe and I did have to readjust the M666 H value anyway, because the 0.8mm was enough to push offsets out of range. It won't be an issue for me recalibrating when I add the heated bed as I understand the calibration process pretty well now.

Yeah I've been throwing up the idea of getting some BuildTak for a while. I've been doing the cheap glue stick thing which helps, but if PLA is curling I can't imagine how bad ABS is going to be. I might try BuildTak while I'm waiting for my heated bed parts to arrive though.

Those results don't look good to me. First, you have an error of around 5mm in all the readings. This suggest to me that you started with the homed height set incorrectly by about 5mm, unless I am missing something. After you have homed the printer but before you run auto calibration, where does the printer think Z=0 is?

Second, the height errors are varying far too much between passes, as if you are getting inconsistent results. Did you reduce the probing and homing speeds as I described in an earlier post? Another possibility is that you have the maximum movement speed set too high and the motors are missing steps when travelling between probe points.

I just checked my delta, by homing it, probing 3 times and reporting the results, then running auto calibration once, then probing another 3 times. These are the results I got (latest at the top):

PS - I just tried removing the homing command from my probe file to make it like yours, and I am getting the same effect - the height errors decrease by about 0.18mm per iteration. Looks to me either like a firmware bug, or the motors are missing steps when they stop after probing. I will investigate.

Perhaps your initial error of nearly 5mm was caused by doing this repeatedly?

I think I've sussed it. When a move is aborted because the Z probe has triggered, I believe the firmware is mis-calculating the stepper motor positions by 1 microstep. On my machine that's 12.5um, so after probing 13 points the error is 13 * 12.5 = 162.5um which is about what I observe.

- Fixed possible divisions by zero in the filament usage calculations, which could lead to AJAX errors from the web interface
- Fixed problem whereby after a sucessful Z probe, the coordinates of the moving motors were miscalculated by 1 microstep
- When using an analog Z probe (e.g. IR sensor), the slow homing speed is no longer the maximum Z jerk speed (as configured by M566), instead it is 1/3 of the normal Z homing speed (as configured by M210)
- Changed the way Z probe results are reported to show the mean and standard deviation separately

This release gives consistent result on my delta. Let me know what results you get on yours.

The dip at about 18 minutes is where I reconfigured marlin to run the bed heater bang-bang, but it didn't help. I'm not sure about the dip at 30 minutes. I was moving the head around using the manual controls about then, so it is possible that the power supply couldn't provide enough current.